Impact of Clenching on Range of Motion of Hip Joint and Lumbar Spine in Rugby Players

Author(s): Mutsumi Takahashi, Yogetsu Bando, Takuya Fukui, Masaaki Sugita

The purpose of this study was to clarify the influence of occlusion on the range of motion of the hip joint and lumbar spine in rugby players. Participants were 39 male rugby players. Cross-test was performed without any instructions regarding occlusion, and participants were divided into that clenched during measurement (occlusal group) and other (non-occlusal group). Next, spinal shape was measured in a static standing position and a standing forward bending position under the conditions of the mandibular rest position (RP) and clenching (CL), and the hip joint range of motion (HJM), lumbar range of motion (LM), and spinal range of motion (SM) were calculated. Differences in HJM, LM, and SM according to participant groups and occlusal conditions were analyzed. Additionally, the reduction rate in range of motion for each alignment due to clenching was calculated, and differences between participant groups and spinal alignment were analyzed. In HJM, LM, and SM, CL was significantly lower than RP in both groups. The reduction rate in HJM was higher in the occlusal group, and that in LM was higher in the non-occlusal group (P<0.01). The greatest reduction rate among spinal alignments was observed in HJM in the occlusal group and in LM in the non-occlusal group (P<0.01). This study suggested that rugby players who clench their teeth during shifting their center of gravity have excellent dynamic balance, and that tend to use their hip joints when flexing their trunk. However, other athletes tended to use their lumbar spine when flexing their trunk.